The effect of first-dose doxorubicin on the cyclic nucleotide levels of the human myocardium

Doxorubicin-induced phosphorylation of lamin A/C enhances DNMT1 and activates cardiomyocyte death via suppressing GATA-4 and Bcl-xL in rat heart

Cardiotoxic effect of Doxorubicin (Dox) limits its clinical application. Previously, we reported that Dox induces phosphorylation of lamin A/C (pS22 lamin A/C), increased nuclear size, damage to the nuclear membrane, and cell death. However, the activation of signalling pathway during this event remains elusive, and it is unclear whether increased phospho-lamin A/C activates the cell death pathway in heart. Here, we demonstrated that Dox-induced lamin A/C phosphorylation causes apoptotic cell death. Increased levels of reactive oxygen species (ROS), DNA methylation and apoptosis markers (Bax, Bid, caspase 3 and caspase 9) were observed in Dox-exposed H9c2 cells. Nuclear membrane damage due to increased pS22 lamin A/C causes increased DNMT1 and DNA methylation followed by reduced expression of GATA-4 and Bcl-xL in Dox-treated H9c2 cells and rat hearts. Further, increased mRNA expression of DNMT1 and reduced expression of GATA-4 and Bcl-xL was observed in H9c2 cells after knocking down of lamin A/C expression. Previously, we reported that N-acetylcysteine improves lamin A/C levels and maintain nuclear membrane integrity. Similarly, in this study Astaxanthin (Ast), a membrane-specific antioxidant, reduces the expression of DNMT1 and phospho-lamin A/C levels; increases mRNA expression of GATA-4 and Bcl-xL; reduces ROS levels and DNA leakage in Dox-treated H9c2 cells and rat hearts. Ast also improves the cardiac structure and function in Dox-treated rats. In conclusion, Dox exposure in cardiomyoblasts and hearts causes cell death by increasing the pS22 lamin A/C, DNA methylation and reducing the expression GATA-4 and Bcl-xL. This study provides a novel pathway for Dox-induced cardiotoxicity and a possible therapeutic approach to reduce it.

Doxorubicin induces phosphorylation of lamin A/C and loss of nuclear membrane integrity: A novel mechanism of cardiotoxicity

Lamin A/C, essential inner nuclear membrane proteins, have been linked to progeria, a disease of accelerated aging, and many other diseases, which include cardiac disorder. Lamin A/C mutation and its phosphorylation are associated with altering nuclear shape and size. The role of lamin A/C in regulating normal cardiac function was reported earlier. In the present study, we hypothesized that Doxorubicin (Dox) may alter total lamin A/C expression and phosphorylation, thereby taking part in cardiac injury. An in vitro cellular injury model was generated with Dox (0.1-10.0 μM) treatment on cardiomyoblast cells (H9c2) to prove our hypothesis. Increased size and irregular (ameboid) nucleus shape were observed in H9c2 cells after Dox treatment. Similarly, we have observed a significant increase in cell death on increasing the Dox concentration. The expression of lamin A/C and its phosphorylation at serine 22 significantly decreased and increased, respectively in H9c2 cells and rat hearts after Dox exposure. Phosphorylation led to depolymerization of the lamin A/C in the inner nuclear membrane and was evidenced by their presence throughout the nucleoplasm as observed by immunocytochemistry techniques. Thinning and perforation on the walls of the nuclear membrane were observed in Dox-treated H9c2 cells. LMNA-overexpression in H9c2 protected the cells from Dox-induced cell death, reversing all changes described above. Further, improvement of lamin A/C levels was observed in Dox-treated H9c2 cells when treated with Purvalanol A, a CDK1 inhibitor and N-acetylcysteine, an antioxidant. The study provides new insight regarding Dox-induced cardiac injury with the involvement of lamin A/C and alteration of inner nuclear membrane structure.

Peptide-Based Hydrogels and Nanogels for Delivery of Doxorubicin

INTRODUCTION

The clinical use of the antitumoral drug doxorubicin (Dox) is reduced by its dose-limiting toxicity, related to cardiotoxic side effects and myelosuppression. In order to overcome these drawbacks, here we describe the synthesis, the structural characterization and the in vitro cytotoxicity assays of hydrogels (HGs) and nanogels (NGs) based on short peptide sequences loaded with Dox or with its liposomal formulation, Doxil.

METHODS

Fmoc-FF alone or in combination with (FY)3 or PEG8-(FY)3 peptides, at two different ratios (1/1 and 2/1 v/v), were used for HGs and NGs formulations. HGs were prepared according to the "solvent-switch" method, whereas NGs were obtained through HG submicronition by the top-down methodology in presence of TWEEN®60 and SPAN®60 as stabilizing agents. HGs gelation kinetics were assessed by Circular Dichroism (CD). Stability and size of NGs were studied using Dynamic Light Scattering (DLS) measurements. Cell viability of empty and filled Dox HGs and NGs was evaluated on MDA-MB-231 breast cancer cells. Moreover, cell internalization of the drug was evaluated using immunofluorescence assays.

RESULTS

Dox filled hydrogels exhibit a high drug loading content (DLC=0.440), without syneresis after 10 days. Gelation kinetics (20-40 min) and the drug release (16-28%) over time of HGs were found dependent on relative peptide composition. Dox filled NGs exhibit a DLC of 0.137 and a low drug release (20-40%) after 72 h. Empty HGs and NGs show a high cell viability (>95%), whereas Dox loaded ones significantly reduce cell viability after 24 h (49-57%) and 72 h (7-25%) of incubation, respectively. Immunofluorescence assays evidenced a different cell localization for Dox delivered through HGs and NGs with respect to the free drug.

DISCUSSION

A modulation of the Dox release can be obtained by changing the ratios of the peptide components. The different cellular localization of the drug loaded into HGs and NGs suggests an alternative internalization mechanism. The high DLC, the low drug release and preliminary in vitro results suggest a potential employment of peptide-based HGs and NGs as drug delivery tools.

Pharmacodynamic modeling of cardiac biomarkers in breast cancer patients treated with anthracycline and trastuzumab regimens

Trastuzumab is associated with cardiotoxicity, manifesting as a decrease of the left-ventricular ejection fraction (LVEF). Administration of anthracyclines prior to trastuzumab increases risk of cardiotoxicity. High-sensitive troponin T and N-terminal-pro-brain natriuretic peptide (NT-proBNP) are molecular markers that may allow earlier detection of drug-induced cardiotoxicity. In this analysis we aimed to quantify the kinetics and exposure–response relationships of LVEF, troponin T and NT-proBNP measurements, in patients receiving anthracycline and trastuzumab. Repeated measurements of LVEF, troponin T and NT-proBNP and dosing records of anthracyclines and trastuzumab were available from a previously published clinical trial. This trial included 206 evaluable patients with early breast cancer. Exposure to anthracycline and trastuzumab was simulated based on available dosing records and by using a kinetic-pharmacodynamic (K-PD) and a fixed pharmacokinetic (PK) model from literature, respectively. The change from baseline troponin T was described with a direct effect model, affected by simulated anthracycline concentrations, representing myocyte damage. The relationship between trastuzumab and LVEF was described by an indirect effect compartment model. The EC₅₀ for LVEF decline was significantly affected by the maximum troponin T concentration after anthracycline treatment, explaining 15.1% of inter-individual variability. In this cohort, NT-proBNP changes could not be demonstrated to be related to anthracycline or trastuzumab treatment. Pharmacodynamic models for troponin T and LVEF were successfully developed, identifying maximum troponin T concentration after anthracycline treatment as a significant determinant for trastuzumab-induced LVEF decline. These models can help identify patients at risk of drug-induced cardiotoxicity and optimize cardiac monitoring strategies.

An integrated characterization of serological, pathological, and functional events in doxorubicin-induced cardiotoxicity

Many efficacious cancer treatments cause significant cardiac morbidity, yet biomarkers or functional indices of early damage, which would allow monitoring and intervention, are lacking. In this study, we have utilized a rat model of progressive doxorubicin (DOX)-induced cardiomyopathy, applying multiple approaches, including cardiac magnetic resonance imaging (MRI), to provide the most comprehensive characterization to date of the timecourse of serological, pathological, and functional events underlying this toxicity. Hannover Wistar rats were dosed with 1.25 mg/kg DOX weekly for 8 weeks followed by a 4 week off-dosing "recovery" period. Electron microscopy of the myocardium revealed subcellular degeneration and marked mitochondrial changes after a single dose. Histopathological analysis revealed progressive cardiomyocyte degeneration, hypertrophy/cytomegaly, and extensive vacuolation after two doses. Extensive replacement fibrosis (quantified by Sirius red staining) developed during the off-dosing period. Functional indices assessed by cardiac MRI (including left ventricular ejection fraction (LVEF), cardiac output, and E/A ratio) declined progressively, reaching statistical significance after two doses and culminating in "clinical" LV dysfunction by 12 weeks. Significant increases in peak myocardial contrast enhancement and serological cardiac troponin I (cTnI) emerged after eight doses, importantly preceding the LVEF decline to <50%. Troponin I levels positively correlated with delayed and peak gadolinium contrast enhancement, histopathological grading, and diastolic dysfunction. In summary, subcellular cardiomyocyte degeneration was the earliest marker, followed by progressive functional decline and histopathological manifestations. Myocardial contrast enhancement and elevations in cTnI occurred later. However, all indices predated "clinical" LV dysfunction and thus warrant further evaluation as predictive biomarkers.

Breast cancer therapies and cardiomyopathy

The prevalence of chemotherapy-related cardiac disease is increasing and management demands a multidisciplinary approach from cardiologists and oncologists. Pretreatment identification of predisposing risk factors and assessment of cardiac function before and at intervals during and after therapy with cardiotoxic agents are necessary. In clinical practice, surveillance is largely performed using transthoracic echocardiography or multi-gated radionuclide angiography. Imaging strategies that detect cardiac injury before overt left ventricular systolic dysfunction provide an opportunity for early intervention and improved cardiac outcomes.

Mechanisms of anthracycline cardiac injury: can we identify strategies for cardioprotection?

Anthracycline antibiotics have saved the lives of many cancer victims in the 50 plus years since their discovery. A major limitation of their use is the dose-limiting cardiotoxicity. Efforts focusing on understanding the biochemical basis for anthracycline cardiac effects have provided several strategies currently in clinical use: limit dose exposure, encapsulate anthracyclines in liposomes to reduce myocardial uptake, administer concurrently with the iron chelator dexrazoxane to reduce free iron-catalyzed reactive oxygen species formation; and modify anthracycline structure in an effort to reduce myocardial toxicity. Despite these efforts, anthracycline-induced heart failure continues to occur with consequences for both morbidity and mortality. Our inability to predict and prevent anthracycline cardiotoxicity is, in part, due to the fact that the molecular and cellular mechanisms remain controversial and incompletely understood. Studies examining the effects of anthracyclines in cardiac myocytes in vitro and small animals in vivo have demonstrated several forms of cardiac injury, and it remains unclear how these translate to the clinical setting. Given the clinical evidence that myocyte death occurs after anthracycline exposure in the form of elevations in serum troponin, myocyte cell death seems to be a probable mechanism for anthracycline-induced cardiac injury. Other mechanisms of myocyte injury include the development of cellular "sarcopenia" characterized by disruption of normal sarcomere structure. Anthracyclines suppress expression of several cardiac transcription factors, and this may play a role in the development of myocyte death as well as sarcopenia. Degradation of the giant myofilament protein titin may represent an important proximal step that leads to accelerated myofilament degradation. An interesting interaction has been noted clinically between anthracyclines and newer cancer therapies that target the erbB2 receptor tyrosine kinase. There is now evidence that erbB2 signaling in response to the ligand neuregulin regulates anthracycline uptake into cells via the multidrug-resistance protein. Therefore, up-regulation of cardiac neuregulin signaling may be one strategy to limit myocardial anthracycline injury. Moreover, assessing an individual's risk for anthracycline injury may be improved by having some measure of endogenous activity of this and other myocardial protective signals.

The CO/HO system reverses inhibition of mitochondrial biogenesis and prevents murine doxorubicin cardiomyopathy

The clinical utility of anthracycline anticancer agents, especially doxorubicin, is limited by a progressive toxic cardiomyopathy linked to mitochondrial damage and cardiomyocyte apoptosis. Here we demonstrate that the post-doxorubicin mouse heart fails to upregulate the nuclear program for mitochondrial biogenesis and its associated intrinsic antiapoptosis proteins, leading to severe mitochondrial DNA (mtDNA) depletion, sarcomere destruction, apoptosis, necrosis, and excessive wall stress and fibrosis. Furthermore, we exploited recent evidence that mitochondrial biogenesis is regulated by the CO/heme oxygenase (CO/HO) system to ameliorate doxorubicin cardiomyopathy in mice. We found that the myocardial pathology was averted by periodic CO inhalation, which restored mitochondrial biogenesis and circumvented intrinsic apoptosis through caspase-3 and apoptosis-inducing factor. Moreover, CO simultaneously reversed doxorubicin-induced loss of DNA binding by GATA-4 and restored critical sarcomeric proteins. In isolated rat cardiac cells, HO-1 enzyme overexpression prevented doxorubicin-induced mtDNA depletion and apoptosis via activation of Akt1/PKB and guanylate cyclase, while HO-1 gene silencing exacerbated doxorubicin-induced mtDNA depletion and apoptosis. Thus doxorubicin disrupts cardiac mitochondrial biogenesis, which promotes intrinsic apoptosis, while CO/HO promotes mitochondrial biogenesis and opposes apoptosis, forestalling fibrosis and cardiomyopathy. These findings imply that the therapeutic index of anthracycline cancer chemotherapeutics can be improved by the protection of cardiac mitochondrial biogenesis.

Adriamycin inhibits PTH-mediated but not PGE2-mediated stimulation of cyclic AMP formation in isolated bone cells

We have examined the effect of adriamycin, an anthracycline antibiotic which modifies plasma membrane functions, on the cyclic AMP response to PTH and PGE2 in isolated osteoblastlike cells. Adriamycin blunted the increment in bone cell cyclic AMP caused by exposure to PTH. This effect appeared rapidly (within 3 min after bone cells were exposed to adriamycin) and disappeared soon after exposure of adriamycin-treated cells to adriamycin-free incubation medium. Inhibition was evident over the entire time course of PTH action, at low as well as high PTH concentrations, and was one-half maximal at 31 microM adriamycin. It could not be attributed to alterations in cyclic AMP exodus, degradation or interference with the cyclic AMP assay, nor to impaired cell viability. Adriamycin also reduced the stimulatory effect of PTH on adenylate cyclase activity in a crude plasma membrane preparation. By contrast, adriamycin failed to modify the effects of PGE2 on cyclic AMP generation in intact bone cells, and on adenylate cyclase activity in broken cells. Moreover, concentrations of adriamycin that blunted the effect of PTH on adenylate cyclase activity did not inhibit the stimulatory effects of sodium fluoride or of GppNHp. These results suggest that adriamycin selectively alters the interaction between PTH and its receptor or impairs the transmission of information from hormone-receptor complex to adenylate cyclase (or both), perhaps by binding to specific lipid domains in the plasma membrane. Structural analogues of adriamycin, which vary in their lipophilic properties, also varied in their capacity to perturb the cyclic AMP response.(ABSTRACT TRUNCATED AT 250 WORDS)